SP-700鈦合金雷射銲件之熱處理及顯微組織研究
Heat Treatment and Microstructural Evolution of SP-700 Laser Welds
Date Issued
2007
Date
2007
Author(s)
Chung, Wei-Chih
DOI
zh-TW
Abstract
The microstructural evolution and heat treatment of SP-700 titanium alloy, in particular the martensitic transformation, have been investigated. The emphasis of this study was also placed on the influence of the post-weld heat treatment (PWHT) on the microstructure and related mechanical properties of SP-700 laser welds. Notched tensile and impact tests of the laser welds with various PWHTs were evaluated. Detailed microstructural and fractographic analyses were conducted on distinct specimens and the results were discussed.
Martensitic transformation studies of SP-700 titanium alloy indicated that β (BCC) was transformed completely into α′ (HCP martensite) after solution treating at a temperature higher than β-transus (approximately 900˚C) and water quenched. The co-existence of α′ and α″ (Orthorhombic martensite) could be observed upon quenching from a temperature which was slightly below β-transus, e.g. 890˚C, of the alloy. Quenching from the intermediate temperature range of 880˚C to 800˚C, the transformation of β to α″ with or without some retained β was resulted according to the solution temperature employed. For a solution temperature of less than 800˚C, β was remained unchanged after rapidly cooling to room temperature. The crystal structure of α″ has been identified as base-centered orthorhombic (centered on C-faces) with
Subjects
SP-700
鈦合金
雷射銲接
銲後熱處理
顯微組織
SP-700 titanium alloy
laser beam welding
heat treatment
microstructure
mechanical properties
Type
thesis
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